dart user input validation code example
Example 1: create a validator in flutter
TextFormField(
// The validator receives the text that the user has entered.
validator: (value) {
if (value.isEmpty) {
return 'Please enter some text';
}
return null;
},
);
Example 2: create a validator in flutter
// Define a custom Form widget.
class MyCustomForm extends StatefulWidget {
@override
MyCustomFormState createState() {
return MyCustomFormState();
}
}
// Define a corresponding State class.
// This class holds data related to the form.
class MyCustomFormState extends State<MyCustomForm> {
// Create a global key that uniquely identifies the Form widget
// and allows validation of the form.
//
// Note: This is a `GlobalKey<FormState>`,
// not a GlobalKey<MyCustomFormState>.
final _formKey = GlobalKey<FormState>();
@override
Widget build(BuildContext context) {
// Build a Form widget using the _formKey created above.
return Form(
key: _formKey,
child: Column(
children: <Widget>[
// Add TextFormFields and ElevatedButton here.
]
)
);
}
}